I think you could try more than one hen, but I would not introduce them at different times. Put the hens with him at the same time. Do not use older hens as they would be more aggressive than young hens or pullets. The best would be hens that have not been with another rooster, but want to mate and would readily squat for the rooster. Would be good if the hens were acquainted with each other, otherwise you could get the hens attacking each other over dominance as well as dealing with the rooster. Young hens with a young rooster. Older hens will often refuse to mate with a young guy, especially if they have been with an older, very dominant rooster. Young ready hens are the best choice in any situation.
I once introduced a beautiful part-bantam rooster into a small flock of older laying hens. He was coloured like a RJF, but was of medium size, larger than a RJF. The hens all challenged him and he had to really assert himself. He was successful. Unfortunately he developed a total hatred for one hen and she had to sleep up in the barn, while he stayed with the other hens down in the chickens' quarters. He never allowed her to rejoin the flock.
Always put the hens into the cock's pen. Try putting the hens into his pen in a cage so that they can become acquainted thru the wire first. Watch them and you will see when they are ready to be together. A hen that is ready to lay will often squat for the rooster, even if he is outside her cage. Release the hens to him one at a time so that they cannot gang up on him. Give him time to establish his dominance with the hen - should not take long - and then release the second hen. Shouldn't take longer than a few minutes, especially if the hens have been caged in his pen where he could interact with them before they were released.
Good luck.